<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box1 {
      display: flex;
      flex-flow: row wrap;

      /* align-content:多行交叉轴对其方式，需要和flex-wrap配合使用 */
      /* align-content: flex-start; */
      /* align-content: flex-end; */
      /* align-content: center; */
      /* align-content: space-around; */

      /* 
        algin-items: 是作用于容器内的每一行在当前交叉轴的对齐位置，如果容器内有好几行，则每一行以每一行的交叉轴作为标准对齐
        align-content：设置容器内部所有行作为一个整体在垂直方向排列方式
      */

      align-content: space-between;
      width: 600px;
      height: 600px;
      background-color: pink;
    }
    .box1 div {
      width: 100px;
      height: 100px;
      border: 1px solid #333;
      box-sizing: border-box;
    }
  </style>
</head>
<body>
  <div class="box1">
    <div>a</div>
    <div>b</div>
    <div>c</div>
    <div>a</div>
    <div>b</div>
    <div>c</div>
    <div>a</div>
    <div>b</div>
    <div>c</div>
  </div>
  <div class="box2">2</div>
  <div class="box3">3</div>
</body>
</html>